1. Field of the Invention
The present invention relates to a gasket for providing a fluid-tight seal in a pipe-to-pipe connection between the bell end of one pipe and the spigot end of another pipe.
2. Description of Related Art
Pipes used in underground pipeline systems, such as municipal sanitary sewer systems and/or storm sewer systems, for example, often include opposite bell and spigot ends, and adjacent pipes are connected to one another by inserting the spigot end of one pipe into the bell end of another pipe. A gasket received within the bell end of one pipe is compressed between the spigot end of another pipe and bell end upon insertion of the spigot end into the bell end to provide a fluid-tight seal between the pipes.
Many plastic pipes include gaskets which are installed within the pipes concurrently with the forming operation of the bell ends according to a process known in the art as the Rieber process. In this process, a gasket having a ramped surface is fitted around a mandrel, and a pipe end which has been heated and softened is pushed over the mandrel and then forced up and over the ramped surface of the gasket before being drawn around a trailing portion of the gasket. When the formed pipe bell end cools, the gasket is retained in place within the bell end and the mandrel is removed.
A disadvantage of these types of gaskets is that they can only be installed within certain types of plastic pipes, and are occasionally prone to being dislodged from the pipe bell end by the pipe spigot end upon insertion of the spigot end into the bell end. In particular, the ramped surface(s) of the gasket, while facilitating formation of the bell end during the Reiber process, may allow the gasket to dislodge from the pipe bell end. Also, if the gasket should become dislodged from the bell end or otherwise fail, the gasket is difficult or impossible to replace in the field, usually requiring the entire pipe section to be discarded.
Other types of gaskets are made entirely of a flexible rubber material and are formed by extrusion, followed by cutting the gasket to length and then splicing the ends of the gasket together to form the annular shape of the gasket. However, these types of gaskets necessarily have a cut length tolerance which effects the uniform diameter of the gaskets. Also, when the extruded material of the gasket is bent into an annulus, the material is placed under tension, which introduces forces into the gasket that could cause the gasket to become more easily dislodged from the groove of a pipe bell end or that might otherwise adversely effect the performance of the gasket.
What is needed is a gasket for pipe-to-pipe connections which is an improvement over the foregoing.